• 동력기계공학회지
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• 제11권3호
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• pp.16-21
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• 2007

Three dimensional numerical study was carried out to investigate the effect of aspect ratio on microchannel flow. We considered five straight rectangular channels with aspect ratios (height/width) 0.2, 0.4, 0.6, 0.8 and 1.0. Nitrogen gas flow was investigated for both slip and noslip wall boundary conditions. Isothermal wall condition was assumed. We used control volume method for this simulation. The slip velocity increases with the increase of aspect ratio. Friction coefficient decreases with the increase of aspect ratio. Slip friction coefficient is lower than noslip friction coefficient. Mass flow rate of slip model is higher than that of noslip model. We compared our results with the experimental result reported in the literature. The agreement was good.

• Nuclear Engineering and Technology
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• 제2권3호
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• pp.163-178
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• 1970

닉켈기 내열합금의 일종인 Rene 41을 76$0^{\circ}C$ 및 87$0^{\circ}C$에서 최고 9300 시간까지 시효열처리한 다음, 5% 내지 20%로 압축변형시켜, 이 합금의 실온에서의 소성변형방식 및 석출입자인 ${\gamma}$'입자와 slip line 간의 상호작용을 전자현미경적 방법으로 관찰연구하였다. 본합금의 slip구조는 $\alpha$황동때와 유사하게｛111｝<110>계에 속하는 단일 slip line으로 구성되어 있었으며, 순알루미늄에서 관찰되는 층상구조는 볼 수 없었다. 또한, slip 구조는 시효조건에 따라 변화한다는 것을 알 수 있었다. 미시효상태뿐만 아니라 과시효상태에 있어서도 Slip line은 여전히${\gamma}$' 석출입자를 통과하였으며, 이 때 석출입자는 지금과 더불어 변형되는 것을 볼 수 있었다. 이 관찰결과를 앞서 발표된 자료와 비교 검토하여 과시효상태에서도 ${\gamma}$'입자는 적어도 일부 지금과 정합되어 있다는 결론을 얻었다.

• Steel and Composite Structures
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• 제48권2호
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1986년도 하계학술대회논문집
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• pp.531-534
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• 1986

• Environmental Engineering Research
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• 제20권4호
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• pp.397-402
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• 2015

SCR has been popularly approved as one of the most effective means for NOx emission control in heavy-duty and medium-duty vehicles currently. However, high urea dosing would lead to ammonia slip. And $NH_3$ sensor for vehicle emission applications has not been popularly used in real applications. This paper presents experimental studies on the diesel engine urea-SCR system by using a double NOx sensor system that is arranged in the downstream of the SCR catalyst based on ammonia cross-sensitivity. It was shown that the NOx conversion efficiency rised as $NH_3/NOx$ increases and the ammonia slip started from the $NH_3/NOx$ equal to 1.4. The increase of temperature caused high improvement of the SCR reaction rate while the space velocity had no obvious change. The ammonia slip was in advance as catalyst temperature or space velocity increase and the ammonia storage reduced as catalyst temperature or space velocity increase. The NOx real-time conversion efficiency rised as the ammonia accumulative storage increase and reached the maximum value gradually.

• 항공우주기술
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• 제8권2호
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• pp.113-121
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• 2009

발사환경 시 작용하는 진동 환경을 지상에서 구현하기 위해 가진 시스템을 이용하고 있다. 진동시험은 수직, 수평 방향에 대해 수행되며, 수평방향 시험의 경우 슬립테이블 시스템과 연계하여 시험을 수행하게 된다. 최근 개발 중인 대형 위성의 경우, 위성과 진동 시험기 사이의 연결 구조물의 하중 및 동적 설계 요구 조건을 만족하기 위하여 수평가진 시스템과 열 특성이 매우 다른 스틸 소재를 이용하여 제작하였다. 본 연구에서는 수평가진 시스템과 열팽창 계수가 다른 소재를 이용하는 대형 구조물의 열 특성 및 모멘트 검증 과정과 발생한 문제점을 개선하고자 적용한 안을 제시하고자 한다.

• 자원환경지질
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• 제28권1호
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• pp.69-77
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• 1995

Tertiary Pohang basin distributed in south western part of the Korean peninsula, is composed of Chunbuk formation as the basal conglomerate, Hakjon formation, Duho formation and intrusive basalt having 15 Ma by absolute age data. The basement of the basin is represented to Cretaceous sedimentary rocks, Hakjon welded tuff and Chilpo welded tuff and rhyolite. The fault systems in the basement of Tertiary Pohang basin are consist of $N20^{\circ}E$ fault, $N60^{\circ}W$ and E-W trend. NNE fault is not only strike-slip but also normal dip-slip. WNW fault has sinistral strike-slip sense and the geometry of E-W fault is strike-slip and normal faults. In the basin, the fault system is represented to $N20^{\circ}E$ strike-slip, E-W normal and NNE thrust faults. By these fault relationship and geometry, it is interpreted that NNE sinistral strike-slip fault and N-S normal faults have acted at the Cretaceous basement. After Miocene NNE dextral strike-slip fault has acted and created E-W normal fault. Progressively Tertiary basin was influenced by the transpression to make thrust and fold, namely inversion tectonics.

• 복합신소재구조학회 논문집
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• 제7권1호
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• pp.25-31
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• 2016

Bond stress between cast-in-place ductile fiber reinforced cementitious composites and CFRP plank were experimentally analyzed. As failure shape, the mixture of failure between CFRP plank and epoxy, and failure between concrete and epoxy was shown. In case of RFCON from the suggested simple bond slip relationship, the maximum average bond stress was 5.39MPa, the initial slope was 104.09MPa/mm, and the total slip length was 0.19mm. PPCON showed the maximum average bond stress of 4.31MPa, the initial slope of 126.67MPa/mm, and the total slip length of 0.26mm, while RFCON+ appeared to have 8.71MPa, 137.69MPa/mm, 0.16mm. PPCON+ had 6.19MPa maximum average bond stress, 121.56MPa/mm initial slope, and 0.34mm total slip length. To comprehend the behavior of composite structure of FRP and concrete, local bond slip relation is necessary, and thus a simple relation is suggested to be easily applied on hybrid composite system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.214-215
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• 2009

The friction is inevitable and unpredictable phenomena, so most mechanical systems are designed to low friction effect by using bearings and lubricants. However, the slip-stick actuator applies the friction force to its movement. The slip-stick mechanism is applied the piezoelectric actuator to overcome short displacement. Fast response of piezoelectric actuator is also good characteristic for the slip-stick mechanism. However, the piezoelectric actuator with slip-stick mechanism isn't common, because its cost and driving voltage are too high. In this paper, a voice-coil actuator with slip-stick mechanism is introduced. The cost and the driving voltage of a voice-coil actuator are much less than the piezoelectric actuator. And a dynamic vibration amplifier is proposed to adjust the dynamic performance of the actuator. By the results of numerical analysis, the feasibility of a dynamic vibration amplifier is verified.

• 한국항행학회논문지
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• 제15권4호
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• pp.502-509
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• 2011

GPS 반송파를 이용한 정밀 항법 수행 시 미지 정수 결정이 필수적이다. 한번 결정된 미지 정수는 사이클 슬립이 발생하지 않는 한 변하지 않는다. 그러나 전파 관측 환경의 변화에 따라 사이클 슬립이 발생하게 되며, 이러한 상황에서 연속적인 항법 정보 제공을 위한 적절한 대응 조치를 취해 주어야 한다. 그러나 이러한 조치들은 매우 번거로우며, 소프트웨어적인 복잡성을 야기 한다는 문제가 있다. 본 논문에서는 미지 정수 유지 및 재검색 과정을 단순화하기 위해 시스템 운동 모델을 이용하여 사이클 슬립에 무관한 위치 제공 기법을 제안하였다. 제안된 방법은 고의적으로 사이클 슬립을 발생시켜 대응 성능을 확인하였으며, 이 결과 사이클 슬립과 무관하게 항법 정보를 제공할 수 있음을 확인하였다.